Nature’s Lawnmowers

The release of 30 goats onto the bluffs of Indian Mounds Park was like a red carpet affair. Their tenders called out the name of each goat as they stepped out of their trailer, only to be met with the excited shrieks of children and the snapping of pictures. The goats were corralled into an enclosure that opened up into the forest bluff. Sure enough, as soon as the herd of goats reached the forest edge they tore into the buckthorn, stripping the leaves away with their teeth and diving deeper into the dense underbrush.

Photo Courtesy of Samuel Geer

The Saint Paul Parks and Recreation Department is experimenting with goats as a method for controlling buckthorn and invasive species in the open spaces above the Mississippi River. There are well documented examples of how this practice can be effective, but it can be tricky to get it right and also begs some larger questions about efforts to contain and manage invasive species.

Buckthorn is a devilish plant, well adapted to thrive in the understory of a forest. It is the first plant to leaf out in the spring and the last to shed them in the fall. The traditional process for managing buckthorn is labor intensive and involves chainsaw work and herbicide application. Intense mechanical disturbance can rapidly mow through a thick stand of buckthorn, but typically compacts the soils and destroys all the desirable vegetation at the same time.

Invasive species present us with a fundamental choice, to fight or not to fight. Left unchecked they can decimate local ecologies and create unsightly or unsafe urban environments. However, once initiated, the fight to suppress them never really stops. Urban habitat patches are typically fragmented and disturbed by human activity, making them challenging environments to “restore.” Hard fought gains can easily be undone by a few years of negligence. Because of this, smart landscape management often involves picking key battles and making a long term commitment to an invasive species control effort.

Goat grazing are new management paradigm that builds on the natural voraciousness of goats as a disturbance regime which can slow the spread of invasive species. This is an enticing new alternative to chemical and intensive mechanical approaches because it has a much lower cost, labor, and carbon footprint and is pesticide free. Despite these benefits the approach is not without its drawbacks, including the potential of goat escape, the theft of goats, predators, and overgrazing.

Photo Courtesy of Samuel Geer

For this project, Saint Paul partnered with Goat Dispatch, a goat rental company out of Faribault that can deploy goats to browse on the woody leaves and vegetation. Their method involves multiple deployments to a site over the course of the growing season to suppress the invasive species. The challenge is that the goats eat not only the buckthorn, but also any desirable vegetation that exists in the vicinity. Goat Dispatch calibrates the number of goats and the size of the enclosed area to achieve the right level of browsing. This ideally will control invasive buckthorn and honeysuckle while extracting the goats before they decimate the rest of the plant population.

It is exciting that cities are moving towards ecological landscape management strategies rather than the wasteful and toxic paradigms embodied by the pesticide and lawn care industries. Strategies like integrated pest management, controlled burns, and goat grazing are less straightforward than these mainstream landcare methods, but once calibrated properly, they can deliver excellent, cost effective results and deliver surprising side benefits. This kind of experiment is necessary to work out the kinks and figure out how to effectively scale these practices up.

Photo Courtesy of Samuel Geer

At the goat release, I was also struck by the novelty of seeing grazing animals in the city, something that is forbidden by many city ordinances. Naturally the novelty would fade with time and familiarity, but goats are much more charismatic than lawnmowers and chainsaws and have the potential to be an iconic representation of a new experimental attitude towards the remnant habitats that we share with the other urban wildlife.

– Buckthorn is supposedly spread by animals eating the berries and then spreading the seed through excrement. Is there a possibility that the goats will similarly re-seed an area?

– The cut & paint method with herbicide supposedly kills off the root system so eventually (2 – 3 years?) an area is fairly free from new growth. Will the root systems die off on their own from goats eating the above ground portion?

We went on Saturday to go see the goats. While we sadly saw none-though we certainly smelled them-it was great to see so many people at Indian Mounds Park looking for goats to. A nice co-benefit of this project will be, at least, people learning about a (relatively) unknown greenspace gem in the city.

The herbicide application on the cut stem approach can have better kill results for sure, but comes with its own set of problems. When I have worked on buckthorn control projects we made an effort to kill the bigger and more mature seed producers, stump treat them and then focus on controlling the regrowth. The benefit of the goats is that they can stay on top of the regrowth.

I have read that the digestive track of a goat can render buckthorn seeds inert, but do not know that this is definitely true. It might just be pro-goat propeganda.

Ultimately, there is not any real way to totally get rid of buckthorn if a seedbed is established. You have to have an ongoing maintenance strategy or it will tend to re-establish.